The effect of thermal annealing on crystallization in a-Si : H/SiO2 multilayers by using layer by layer plasma oxidation

摘要

Two post-treatments consisting of rapid thermal annealing (RTA) and furnace annealing (FA) were used to crystallize a-Si:H sublayers in a-Si:H/SiO2 multilayers fabricated by alternate plasma-enhanced chemical vapour deposition of a-Si:H layers and plasma oxidation. Raman measurements show that the crystallization process of a-Si:H sublayers strongly depends on the post-treatment process. RTA is advantageous for nucleation, in which the size of the nuclei increases with higher annealing temperatures, and the crystalline volume ratio increases with longer annealing times. In FA, however, higher temperatures are required for further crystallization such as increasing the grain size and crystalline volume ratio. The ultimate size of nc-Si grains can be accurately determined by the thickness of the a-Si:H sublayer. Moreover, the mechanism of the constrained crystallization will also be discussed in accordance with the thermodynamic theory. [References: 15]